#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	char a = 0;
	scanf("%c", &a);
	if (a >= 'a' && a <= 'z' || a >= 'A' && a <= 'Z')
	{
		printf("YES");
	}
	else
	{
		printf("NO");
	}
	return 0;
}